The present invention relates to a process for the preparation of .alpha.-aspartyl phenylalanine methyl ester.
.alpha.-aspartyl phenylalanine methyl ester (or aspartam) is in great demand as an anti-caloric artificial sweetening agent. Its pharmacological and toxicological properties are now well known and its use does not involve any of the risks ascribed to the use of products such as saccharine and cyclohexylsulfamate.
It is also known that said aspartam should be used in its isomer form, because its .beta.-isomer has no sweetening power and is on the contrary bitter in flavor.
It is therefore desirable to find a simple process for the synthesis of said aspartam, such process permitting to minimize the production of undesirable by-products (such as said .beta.-isomer) and comprising a valorizing technique by conversion of said .beta.-isomer into an .alpha.-isomer.